1. Technical Field
The present disclosure relates to a loudspeaker diaphragm and a loudspeaker for various audio devices.
2. Description of the Related Art
Loudspeaker diaphragms are roughly classified into cellulose diaphragms and resin ones. Cellulose diaphragms are produced by subjecting cellulose fibers to a paper-making process, whereas resin diaphragms are produced by injecting resin into a mold. Some kinds of loudspeakers are used under severe conditions, such as in a vehicle engine compartment or in a vehicle interior. Most of such loudspeakers include a resin diaphragm made from polypropylene as base resin in terms of waterproofness, cost, and specific gravity. Polypropylene is a kind of thermoplastic resin.
Japanese Unexamined Patent Application Publication No. H03-85100 (hereinafter, Patent Literature 1) discloses the following loudspeaker diaphragms (1) and (2):    (1) A loudspeaker diaphragm produced by accumulating ceramic powder or metal powder onto a diaphragm base formed by molding a molybdenum foil or a polyimide resin film, and depositing a diamond film layer onto the surface of the accumulated powder.    (2) A loudspeaker diaphragm produced by removing the above-mentioned diaphragm base after the deposition of the diamond film layer.
Meanwhile, Japanese Patent No. H07-101957 (hereinafter, Patent Literature 2) discloses the following loudspeaker diaphragms (3) to (5):    (3) A loudspeaker diaphragm produced by depositing a diamond layer onto a diaphragm base, and then removing the diaphragm base.    (4) A loudspeaker diaphragm produced by depositing a mixture layer containing diamond-like carbon and diamond onto a diaphragm base, and then removing the diaphragm base.    (5) A loudspeaker diaphragm produced by depositing a diamond layer onto a diaphragm base, depositing a diamond-like carbon layer onto the diamond layer, depositing a diamond layer onto the diamond-like carbon layer, and removing the diaphragm base.